All this noise around "back to the roots" template rendering seems to ignore the elephant in the room that FE devs DON'T want to work with jinja2, django templates and all this jazz as it is perceived as a devaluation of the role + they need to learn specific syntaxes instead of having a "one size fits all" approach like with js frameworks.
JavaScript is eventually needed for any non-trivial app. JS without a build system/dependency management is a maintenance nightmare. JS without linting, TypeScript, module syntax and unit tests is a maintenance nightmare.
Reuse of components is much easier and more testable with framework abstractions (compare a react/vue/svelte component to e.g. a laravel blade component).
Strict separation of CSS, HTML and JS means things like class names drift. With a JS build system you can easily introduce tooling to combat this (auto-removal of unused styles, enforcing that all classes are used, linting for CSS code, etc).
I just can't imagine building an app of more than a few thousand lines without a framework and frontend build tooling. I would end up needing to reinvent these tools myself to ensure code quality as the project grows. I'm not saying it's impossible to add these features into, say, a Django or Rails app, just that it's more work for a worse outcome.